NO814364L - NEW PHENOXYALCOXY-SUBSTITUTED SILANES AND PROCEDURES IN THEIR PREPARATION - Google Patents

Description

The present invention relates to silane monomers. More specifically, it relates to phenoxyalkyloxy-substituted silanes. The invention relates in particular to alkyl- or alkenyl-tris-(phenoxyalkyloxy)-silanes and -tetrakisphenoxyalkyloxysilanes.

Organosilanes have found widespread use as lubricants, hydraulic fluids, coupling agents in polymer materials with mineral fillers, water repellants, additives for electrically insulating polymer materials to delay "wood pattern" structure degradation, and intermediates in the manufacture of organopolysiloxanes.

US Patent No. 2,559,342 describes a

class of hydrocarbyl oxyethoxysilanes which are produced by reacting organochlorosilanes with alkoxyethanols.

According to US Patent No. 3,814,691, organosilanes are used as the base material for a hydraulic fluid. These silanes have the general formula:

where R is alkyl with 1-10 carbon atoms or aryl with 6-10 carbon atoms, R<1>is alkyl with 1-4 carbon atoms,

R" is the alkylene with 2-4 carbon atoms, y is a number from 1

to 5, and z is a number from 1 to 3. Only nine compounds of the above formula are specifically indicated, and of these only two exemplify a compound in which a single alkylene group is present. In both of these cases, the silane is a dimethylsilane. None of the silanes described in US patent documents Nos. 3,048,499 and 2,851,474 contain any aryl groups, while all of the organic groups are aryl groups in the silanes according to British patent document no.

953 421. The most relevant compounds covered by the broad general formula given in US Patent No. 4 141 851 have two Si-C bonds and two Si-O-C bonds from the only Si atom.

The method used in accordance with US Patent No. 2,559,342 for the production of the organosilanes described therein involves the reaction of an organochlorosilane with a 2-alkoxyethanol under reflux conditions, until the evolution of HC1 has ended. In US patent 3,814,691, the silanes described there are prepared by reacting an alkylhalosilane with polyalkylene glycol monoalkyl or monoaryl ethers in an inert medium.

US patent application no. 161 932 describes the addition of organosilanes to polymer materials in order to

increase resistance to the phenomenon known as electricity-induced "wood-patterning" and water-induced "wood-patterning". These materials are applicable as insulating materials for electrical cables.

Polymer materials are well known and are widely used as insulating materials for wires and cables. For use as insulation materials, it is important that the material has certain physical and electrical properties, such as resistance to mechanical cutting, resistance to cracking due to voltage stresses and resistance to dielectric failure. Recent publications have shown that water-induced wood-patterning and electricity-induced wood-patterning in the insulation are particularly important problems, because they are associated with, although not solely responsible for, dielectric failure

The terms "tree" and "tree pattern" have been used for this type of insulation breakdown, because the point of failure is a cavity in appearance like the profile of a tree, ie in the shape of a tree trunk and its upper branches. Tree pattern formation is usually a phenomenon that develops slowly, and it can take years before a failure of the insulation occurs.

An important area of application for insulating materials is high-voltage transmission and distribution cables, especially earth cables. Two types of tree-patterning have been observed in these power lines, namely electricity-induced tree-patterning and water-induced tree-patterning, which is sometimes referred to as electrochemical tree-patterning. It is commonly assumed that electricity-induced tree pattern formation occurs through corona discharges which cause melting and breakdown of the polymer, while water-induced tree pattern formation usually occurs in cables that are buried in moist ground. The water-caused wood-like patterns have a different appearance to the electricity-caused wood-like patterns. Metal ions are usually found in the water-induced wood patterns.

US Patent No. 4,144,202 is concerned with preventing electrical breakdown of the electrical insulating ability of dielectric materials based on ethylene polymers, as a result of water-induced wood pattern formation. As stated in the patent document, the water-induced wood pattern formation in the ethylene polymer materials is inhibited by the use of organosilane compounds with an epoxy group-containing radical. In TE-OS 2 737 430 it is stated that the addition of certain alkoxysilanes to polyolefin insulation materials prevents water-induced wood pattern formation. US Patent Application No. 161,932, filed June 23, 1980, describes a variety of organosilanes that are useful as additives to delay wood pattern formation. Those which are particularly preferred contain at least one group -CX^H^-O-R, where R is alkyl or aryl. Vinyl-tris-(2-phenoxyethoxy)-silane is indicated specifically and is used as an example of a useful additive for polymeric insulating materials in view. to delay the occurrence of water-caused and electricity-caused wood pattern formation.

According to the present invention, materials are provided which are particularly useful as additives to delay water-induced wood pattern formation and electricity-induced wood pattern formation. Two particularly preferred compounds are methyl-tris-(2-phenoxyethoxy)-silane and v-vinyl-tris-(2-phenoxyethoxy)-silane. The materials according to the invention correspond to the general formula:

where R is alkyl with 1-5 carbon atoms, alkenyl with 1-4

carbon atoms or —(—O-C H~ ■} O- Y v i

y is an integer from 1 to 5 and n is an integer from 1 to 4.

The invention also relates to a method for producing these compounds.

This method is a method for producing an organosilane corresponding to the formula:

where R is alkyl with 1-5 carbon atoms, alkenyl with 2-4 carbon atoms carbon atoms, or from 1 to 5 and n is an integer. from 1 to 4, whereby one: (a) converts an alcohol of formula:

with a halosilane of the formula (C-^-C^-alkyl)SiX2 when R is alkyl of 1-5 carbon atoms, (G2-C^-alkenyl)SiX^ when R is alkenyl of 2-4 carbon atoms. or SiX^when R is

where X is a halogen atom and n and y have the meanings given above, in the presence of a hydrogen halide acceptor and an inert solvent. (b) separating the hydrogen halide acceptor containing hydrogen halide from the reaction mixture, and (c) isolating a compound of the formula R-Si-HO-CnH2n-)-^0-^^: ]3 from the reaction mixture.

The invention relates to a class of tris- or tetrakis-(phenoxyalkyloxy)-silanes and one process for their preparation. Briefly, these silanes are described as C1-C5-alkyl- or C2-C4-alkeny.1-tris- or tetrakis-

(phenoxyalkoxy)-silanes, especially tris-(2-phenoxyethoxy)-silanes. Phenoxypolyalkoxysilanes are also included among the silanes according to the invention.

In the general formula used here for

to represent these silanes, R can for example be an alkyl group, such as methyl. ethyl, propyl, isopropyl, butyl, isobutyl, amyl and the like or an alkenyl group such as vinyl, 1-methyl-vinyl, allyl, butenyl-1, -2- or -3 and the like. Then n in the group cnH2n ^an be ^ra ^ t:"-l ^'^an -CH2-, -CH2-CH2-, CH2-CH(CH3)-, -CH2-CH2-CH2-, -CH2-CH2CH- (CH3)-, or -CH2-CH2-CH2-CH2- make up this part of the formula. In the tetraxysilanes according to the invention, R is a phenoxyalkyloxy group as described below. Although the two specific silanes specified above, namely methyl-tris-(2-phenoxyethoxy )-silane and vinyl-tris-(2-phenoxyethoxy)-silane, can be prepared relatively easily and are therefore the preferred compounds, other examples of the compounds according to the invention are ethyl-tris-(phenoxymethoxy)-silane, vinyl-tris-( 3-phenoxypropoxy)-silane, propyl-tris-(4^-phenoxybutoxy)-silane, methyl-tris-(1-methyl-2-phenoxyethoxy)-silane, allyl-tris-(1-methyl-3-phenoxypropoxy) .)-silane, tetrakis-(2-phenoxyethoxy)-silane and likewise the phenoxypolyalkoxysilanes, such as vinyl-tris-(phenoxyethoxyethoxy)-silane, vinyl-tris-(phenoxytri-ethoxy)-silane and the like.

The silanes according to the invention find many uses, for example as coupling agents in polymer materials with mineral fillers, as additives in polymer materials for electrical insulation with a view to delaying water-induced wood pattern formation and electricity-induced wood pattern formation and as intermediate products for the production of organopolysiloxanes.

The present silanes can be prepared by reacting an organotrihalosilane or tetrahalosilane with a phenoxy-C₁-C₁-alkanol. The preparation can be carried out by bringing the reactants together in an organic solvent, such as toluene, xylene and the like, and the mixture is heated under reflux conditions until the evolution of hydrogen halide has ended. The desired silane can then be separated by distillation, e.g. vacuum distillation. In a particularly effective embodiment, a hydrogen halide acceptor is added, such as pyridine, dimethylaniline or the like,

to the reaction mixture to remove the hydrogen halide at a low temperature, namely at the temperature of 0 - 15° C. Pyridine or dimethylaniline hydrogen halide forms a precipitate which can be removed by filtration after the reaction is complete. In this way, one avoids boiling the mixture with reflux cooling during the reaction. The recovery of the silane is carried out by distillation in the same way as stated above.

In accordance with the general formula for the silanes in question, the halosilane reactant is a (C 1 -C 4 -alkyl)-halosilane, a (C 2 -C 4 -alkenyl)-halosilane or a tetrahalosilane. Preferably, the halogen is chlorine. The phenoxy-C1-C3-alkanol has the general formula:

where y and n have the meanings indicated in connection with the silane formula. Examples of applicable halogenosilanes are tetrachlorosilanes, methyltrichlorosilane, methyltribromosilane, ethyltrichlorosilane, propyltrichlorosilane, n-butyltrichlorosilane, n-amyltrichlorosilane, vinyltrichlorosilane, allyltrichlorosilane, butenyltrichlorosilane and the like. The applicable phenoxyalkanols include phenoxymethanol, 2-phenoxyethanol, 3-phenoxypropanol-1, 4- phenoxybutanol-1, l-methyl-2-phenoxyethanol, l-methyl-3-phenoxypropanol-1, phenoxyethoxyethanol, phenoxydiethoxyethanol and the like, as well as mixtures thereof. Some of these alcohols can also be described as phenyl ethers of ethylene glycol, trimethylene glycol, tetramethylene glycol, propylene glycol and n-butylene glycol.

In the production of the preferred silanes, the 2-phenoxyethanol used often contains small amounts of phenoxyethoxyethanol and phenoxydiethoxyethanol, which results in a product containing small amounts of the silanes corresponding to these ethoxyethanols. A person skilled in the art will understand that the term phenoxy-C₁-C₁-alkanol used here is intended to include phenoxyalkanols containing small amounts of the homologous alkoxy and diethoxy compounds.

The following examples illustrate the invention.

Example 1

Vinyl-tris-(2-phenoxyethoxy)-silane was prepared by the following reaction:

In a 1 liter round-bottomed flask equipped with a cooler, thermometer, mechanical stirrer and dropping funnel and protected from atmospheric moisture, 0.6 mol of phenylcellosolv (also known as 2-phenoxyethanol), 0.65 mol of dry pyridine and 300 ml of toluene. The flask was cooled to 5°C, and a mixture of 0.2 mol of vinyltrichlorosilane in 100 ml of toluene was added dropwise, maintaining a temperature lower than 15°C in the flask. After the addition was complete, the flask was allowed to reach room temperature, and this temperature was maintained for 4 hours.

The precipitate of pyridine hydrochloride was filtered off and washed with toluene. The toluene, which contained the product, was removed under vacuum in a rotary evaporator.

The residue was distilled at 254 - 256° C and

0.8mmHg. The yield was 82.64%. The recovered material proved by spectroscopy in the infrared range to be vinyl-tris-(2-phenoxyethoxy)-silane.

Example 2

Methyl-tris-(2-phenoxyethoxy)-silane was prepared according to the following equation:

To the apparatus described in example 1, 0.75 mol of phenylcellosolve, 0.80 mol of dry pyridine and 400 ml of dry toluene were added. The flask was cooled to 5° C, and a mixture of 0.25 mol of methyltrichlorosilane in 100 ml of toluene was slowly added from a dropping funnel. The temperature was kept below 10° C. throughout the addition. The flask was then allowed to warm to room temperature and was held at room temperature for 3 hours.

The white precipitate of pyridine hydrochloride was separated from the solution by filtration, and the toluene was removed under vacuum in a rotary evaporator. The product was purified by distillation at 256-258°C and 1 mmHg. The yield was 80%. The recovered material was identified as methyl-tris-(2-phenoxyethoxy)-silane by spectroscopy in the infrared region.

Example 3

The properties of the silanes prepared in Examples 1 and 2 with regard to inhibiting water-induced wood pattern formation and electricity-induced wood pattern formation were assessed by means of a series of accelerated tests.

The material samples were prepared by grinding a commercial polyethylene and a small amount of the wood-pattern formation-inhibiting additive to be tested in a 2-roll mill at approx. 149° C for approx. 10 minutes, so that a homogeneous dispersion was obtained. The crab obtained was then used for the production of test pieces for testing with regard to electricity-induced wood pattern formation and water-induced wood pattern formation using the methods described below. All of the materials comprised a commercial polyethylene with a melt index of approx. 0.20-0.35 g/10 min and a density of approx. 0.917 g/cm and contained the wood-inhibiting additive in the amounts indicated in Table I. The control sample did not contain any wood-inhibiting additive.

In order to determine the applicability and effectiveness of the polymeric materials containing the silanes according to the invention with regard to the inhibitory effect on water-induced wood pattern formation and electricity-induced wood pattern formation, the materials were examined by means of accelerated tests.

The tests with a view to investigating the inhibition of electricity-induced wood pattern formation were carried out using a method similar to the method according to ASTM 3756. Strips of the test material of width approx. 25.4 mm. was cut from a 6.35 mm thick die-cast plate. The block was machined, so that a strip with parallel squares spaced 25.4 mm apart was obtained. The strip was then cut into blocks of squares 25.4 mm x 25.4 mm.

A blunt needle and a sharp needle were pressed into opposite parallel side edges, at elevated temperatures, so that the needle tips were spaced 3.175 mm apart. The introduction of the needles and the cooling of the test piece were carried out slowly to avoid creating thermal or mechanical stresses in the test piece. The sharp needle had a tip diameter of approx. 0.00508 mm, while the diameter of the blunt needle was 0.0508 mm. Eight test pieces were produced and tested simultaneously for each material. The test for judging electricity-induced wood pattern formation was performed by energizing the sharp needle at 15 KV using a frequency of 60 Hz. The blunt needle was grounded. The time it took for each of the eight test pieces to fail as a result of tree pattern formation, with subsequent electrical short circuit, was noted. The time it took for 50% of the test pieces to fail was used as a measure of the effectiveness of the tested wood patterning inhibitor.

The test for assessing water-induced wood pattern formation was carried out according to a method similar to that described in US patent document no. 4 144 202. A pressure-molded disc of diameter approx. 150 mm with 10 conical countersinks were produced from each material. The shape of the disc and the dimensions of the recesses were mainly as shown in US patent no. 4 144 202. The underside of the disc was sprayed with a silver paint which was to serve as the grounded electrode. A 150.4 mm long tube of acrylic plastic was clamped to the upper side of the disc, so that a test cell was formed. About. 150 ml of 0.01 N sodium chloride solution was poured into the cell and the air bubbles formed on the surface of the sample were removed. A ring of platinum wire was then immersed in the electro-listen and connected to the current source, which delivered 5 KV at a frequency of 3 KHz. The test pieces were energized for 22 hours, after which they were removed from the test cell and washed with distilled water. The ten recesses were cut out of the plate and colored to make the water-induced wood patterns more visible. Thin sections were prepared using a microtome. These were then examined through a microscope (200X), and the wood pattern size measured. Normally, four slices of each sample material were produced, so that the average wood pattern size could be calculated from forty individual measurements. For evaluation of: the different wood-inhibiting agents, the relative wood pattern size was determined by comparison with the average wood pattern size obtained with a standard thermoplastic high-voltage insulating material containing no wood-inhibiting additives.

The results of the tests, for determining the electricity-induced wood pattern formation and the water-caused wood pattern formation, are listed in Table I. All parts and percentages are on a weight basis, unless otherwise stated.

Claims (10)

1. Material, characterized in that it comprises a compound of the general formula: where R is alkyl with 1-5 carbon atoms, alkenyl with 2-4 carbon atoms or , y is an integer numbers from 1 to 5 and n is an integer. from 1 to 4. 2. Material according to claim 1, characterized in that R is methyl or ethyl, y is 1 and n is 2. 3. Material according to claim 1, characterized in that R is vinyl, y is 1 and n is 2 or 3. 4. Material according to claim 1, characterized in that R is methyl, y is 1 and n is 3. 5. Material according to claim 1, characterized in that R is , y is 1 and n is 2. 6. Material according to claim 1, characterized in that R is vinyl, y is 2 or 3 and n is 2. 7. Procedure for the preparation of an organosilane of the general formula: where R is alkyl with 1-5 carbon atoms, alkenyl with 2-4 carbon atoms or , y is an integer from 1 to 5 and n is an integer • from 1 to 4, characterized by: (a) reacting an alcohol of formula: with a halosilane of the formula (C^-C^ alkyl)SiX^ when R is alkyl of 1-5 carbon atoms, (C2-C4 alkenyl)SiX^ when R is alkenyl of 2-4 carbon atoms or SiX^ when R is where X is a halogen atom and n and y have the meanings given above, in the presence of a hydrogen halide acceptor and an inert solvent, (b) separating the hydrogen halide acceptor containing hydrogen halide from the reaction mixture, and (c) isolates a compound of the formula ]^ from the reaction mixture. 8. Method according to claim 7, characterized in that R is methyl, y is 1, n is 2 and X is chlorine. 9. Method according to claim 7, characterized in that R is vinyl, y is 1 or 2, n is -2 and X is chlorine. 10. Method according to claims 7-9, characterized in that pyridine or dimethylaniline is used as hydrogen halide acceptor.